Composition intended to be applied in steels for corrosion protection of their surfaces and process for preparing the same

Abstract

The invention is related to a composition destined to protect steels against corrosion by utilization of the steel's own rust as a passivating element, the rust being removed from the steel and/or being synthetically prepared and agglutinated with a resin, where the resin can have or cannot have as an electric conductivity promoter material an intrinsically conductor polymer (ICP), in this case polyaniline, in its conducting form (emeraldine salt) or non conducting (emeraldine base), besides filler(s) and a dispersant oil.

1. Composition destined to be applied on steels for protection of their surfaces against corrosion, comprising from 45 to 60% by weight of a rust which is the own natural rust of steel or a synthetically prepared rust with the same chemical composition of the referred natural rust, from 35 to 45% by weight of an agglutinant resin, from 2 to 10% of polyaniline, from 2 to 5% of filler and from 0.5 to 2% of dispersant oil. 
     
     
       2. Composition according to  claim 1 , characterized by in an urban and/or industrial atmosphere the rust is composed basically of magnetite (Fe 3 O 4 ), lepidocrocite (γ-FeOOH) and goethite (α-FeOOH). 
     
     
       3. Composition according to  claim 1 , characterized by in a marine atmosphere the rust is composed basically of magnetite (Fe 3 O 4 ), akaganeite (β-FeOOH), goethite (α-FeOOH) and lepidocrocite (γ-FeOOH). 
     
     
       4. Composition according to  claim 1 , characterized by in a rural atmosphere the rust is composed basically of magnetite (Fe 3 O 4 ). 
     
     
       5. Composition according to  claim 2 , characterized by the rust comprises amorphous matter. 
     
     
       6. Process for preparation of a composition according to  claim 1 , characterized by the steel natural rust is removed through a mechanical procedure and rust agglutination occurs with the addition a suitable agglutinant resin, where polyaniline is added, a filler is added and a dispersant oil is added to give fluidity to the composition, where the amount of rust in the composition can be totally or partially constituted of a synthetic material having the same basic composition of the steel natural rust. 
     
     
       7. Process according to  claim 6 , characterized by the synthetic material includes magnetite obtained by the Fe 3 O 4  and Fe 2 (SO 4 ) 3  mixture, acidifying with H 2 SO 4  1 N to about pH=2.0 in a oxygen free environment; followed by solution alkalinization to about pH=10 with NaOH 1 M. 
     
     
       8. Process according to  claim 6 , characterized by the synthetic material includes goethite (α-FeOOH) obtained by slow oxidation of a ferrous hydroxide Fe(OH) 2  solution, free of oxygen, being the Fe(OH) 2 , for its turn obtained by the FeSO 4  and NaOH mixture, the Fe(OH) 2  oxidation is filtered and the residue is dried in an oven. 
     
     
       9. Process according to  claim 8 , characterized by to obtain lepidocrocite (γ-FeOOH) the oxygenation at the last oxidation step of the Fe(OH) 2  suspension is considerably increased. 
     
     
       10. Process according to  claim 6 , characterized by the synthetic material includes akaganeite (β-FeOOH) obtained by FeCl 3  hydrolysis in solution and further drying. 
     
     
       11. Process according to  claim 8 , characterized by to obtain the amorphous matter, the oxygenation is drastically reduced at the last oxidation step of the Fe(OH) 2  suspension. 
     
     
       12. Process according to  claim 6 , characterized by the composition is passed in a mill, until a granularity superior or equal to 150 mesh, before the mixture with the resin. 
     
     
       13. Process according to  claim 12 , characterized by the milled and mixed composition is passed in another mill for homogenization. 
     
     
       14. Composition according to  claim 3 , characterized by the rust comprises amorphous matter. 
     
     
       15. Composition according to  claim 4 , characterized by the rust comprises amorphous matter.